Re: [PATCH v3 09/19] ublk: implement integrity user copy

[Ming Lei <ming.lei@redhat.com>]

On Mon, Jan 05, 2026 at 05:57:41PM -0700, Caleb Sander Mateos wrote:
> From: Stanley Zhang <stazhang@purestorage.com>
> 
> Add a function ublk_copy_user_integrity() to copy integrity information
> between a request and a user iov_iter. This mirrors the existing
> ublk_copy_user_pages() but operates on request integrity data instead of
> regular data. Check UBLKSRV_IO_INTEGRITY_FLAG in iocb->ki_pos in
> ublk_user_copy() to choose between copying data or integrity data.
> 
> Signed-off-by: Stanley Zhang <stazhang@purestorage.com>
> [csander: change offset units from data bytes to integrity data bytes,
>  test UBLKSRV_IO_INTEGRITY_FLAG after subtracting UBLKSRV_IO_BUF_OFFSET,
>  fix CONFIG_BLK_DEV_INTEGRITY=n build,
>  rebase on ublk user copy refactor]
> Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> ---
>  drivers/block/ublk_drv.c      | 52 +++++++++++++++++++++++++++++++++--
>  include/uapi/linux/ublk_cmd.h |  4 +++
>  2 files changed, 53 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index e44ab9981ef4..9694a4c1caa7 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -621,10 +621,15 @@ static inline unsigned ublk_pos_to_tag(loff_t pos)
>  {
>  	return ((pos - UBLKSRV_IO_BUF_OFFSET) >> UBLK_TAG_OFF) &
>  		UBLK_TAG_BITS_MASK;
>  }
>  
> +static inline bool ublk_pos_is_integrity(loff_t pos)
> +{
> +	return !!((pos - UBLKSRV_IO_BUF_OFFSET) & UBLKSRV_IO_INTEGRITY_FLAG);
> +}
> +

It could be more readable to check UBLKSRV_IO_INTEGRITY_FLAG only.

>  static void ublk_dev_param_basic_apply(struct ublk_device *ub)
>  {
>  	const struct ublk_param_basic *p = &ub->params.basic;
>  
>  	if (p->attrs & UBLK_ATTR_READ_ONLY)
> @@ -1047,10 +1052,37 @@ static size_t ublk_copy_user_pages(const struct request *req,
>  			break;
>  	}
>  	return done;
>  }
>  
> +#ifdef CONFIG_BLK_DEV_INTEGRITY
> +static size_t ublk_copy_user_integrity(const struct request *req,
> +		unsigned offset, struct iov_iter *uiter, int dir)
> +{
> +	size_t done = 0;
> +	struct bio *bio = req->bio;
> +	struct bvec_iter iter;
> +	struct bio_vec iv;
> +
> +	if (!blk_integrity_rq(req))
> +		return 0;
> +
> +	bio_for_each_integrity_vec(iv, bio, iter) {
> +		if (!ublk_copy_user_bvec(&iv, &offset, uiter, dir, &done))
> +			break;
> +	}
> +
> +	return done;
> +}
> +#else /* #ifdef CONFIG_BLK_DEV_INTEGRITY */
> +static size_t ublk_copy_user_integrity(const struct request *req,
> +		unsigned offset, struct iov_iter *uiter, int dir)
> +{
> +	return 0;
> +}
> +#endif /* #ifdef CONFIG_BLK_DEV_INTEGRITY */
> +
>  static inline bool ublk_need_map_req(const struct request *req)
>  {
>  	return ublk_rq_has_data(req) && req_op(req) == REQ_OP_WRITE;
>  }
>  
> @@ -2654,10 +2686,12 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter *iter, int dir)
>  {
>  	struct ublk_device *ub = iocb->ki_filp->private_data;
>  	struct ublk_queue *ubq;
>  	struct request *req;
>  	struct ublk_io *io;
> +	unsigned data_len;
> +	bool is_integrity;
>  	size_t buf_off;
>  	u16 tag, q_id;
>  	ssize_t ret;
>  
>  	if (!user_backed_iter(iter))
> @@ -2667,10 +2701,11 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter *iter, int dir)
>  		return -EACCES;
>  
>  	tag = ublk_pos_to_tag(iocb->ki_pos);
>  	q_id = ublk_pos_to_hwq(iocb->ki_pos);
>  	buf_off = ublk_pos_to_buf_off(iocb->ki_pos);
> +	is_integrity = ublk_pos_is_integrity(iocb->ki_pos);

UBLKSRV_IO_INTEGRITY_FLAG can be set for device without UBLK_F_INTEGRITY,
so UBLK_F_INTEGRITY need to be checked in case of `is_integrity`.

>  
>  	if (q_id >= ub->dev_info.nr_hw_queues)
>  		return -EINVAL;
>  
>  	ubq = ublk_get_queue(ub, q_id);
> @@ -2683,21 +2718,31 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter *iter, int dir)
>  	io = &ubq->ios[tag];
>  	req = __ublk_check_and_get_req(ub, q_id, tag, io);
>  	if (!req)
>  		return -EINVAL;
>  
> -	if (buf_off > blk_rq_bytes(req)) {
> +	if (is_integrity) {
> +		struct blk_integrity *bi = &req->q->limits.integrity;
> +
> +		data_len = bio_integrity_bytes(bi, blk_rq_sectors(req));
> +	} else {
> +		data_len = blk_rq_bytes(req);
> +	}
> +	if (buf_off > data_len) {
>  		ret = -EINVAL;
>  		goto out;
>  	}
>  
>  	if (!ublk_check_ubuf_dir(req, dir)) {
>  		ret = -EACCES;
>  		goto out;
>  	}
>  
> -	ret = ublk_copy_user_pages(req, buf_off, iter, dir);
> +	if (is_integrity)
> +		ret = ublk_copy_user_integrity(req, buf_off, iter, dir);
> +	else
> +		ret = ublk_copy_user_pages(req, buf_off, iter, dir);
>  
>  out:
>  	ublk_put_req_ref(io, req);
>  	return ret;
>  }
> @@ -3931,11 +3976,12 @@ static struct miscdevice ublk_misc = {
>  static int __init ublk_init(void)
>  {
>  	int ret;
>  
>  	BUILD_BUG_ON((u64)UBLKSRV_IO_BUF_OFFSET +
> -			UBLKSRV_IO_BUF_TOTAL_SIZE < UBLKSRV_IO_BUF_OFFSET);
> +			UBLKSRV_IO_BUF_TOTAL_SIZE +
> +			UBLKSRV_IO_INTEGRITY_FLAG < UBLKSRV_IO_BUF_OFFSET);

Maybe it can be simplified as:

BUILD_BUG_ON(UBLK_INTEGRITY_FLAG_OFF >= 63);  /* Must fit in loff_t */

>  	BUILD_BUG_ON(sizeof(struct ublk_auto_buf_reg) != 8);
>  
>  	init_waitqueue_head(&ublk_idr_wq);
>  
>  	ret = misc_register(&ublk_misc);
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index c1103ad5925b..3af7e3684834 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -132,10 +132,14 @@
>  #define UBLK_MAX_NR_QUEUES	(1U << UBLK_QID_BITS)
>  
>  #define UBLKSRV_IO_BUF_TOTAL_BITS	(UBLK_QID_OFF + UBLK_QID_BITS)
>  #define UBLKSRV_IO_BUF_TOTAL_SIZE	(1ULL << UBLKSRV_IO_BUF_TOTAL_BITS)
>  
> +/* Copy to/from request integrity buffer instead of data buffer */
> +#define UBLK_INTEGRITY_FLAG_OFF UBLKSRV_IO_BUF_TOTAL_BITS
> +#define UBLKSRV_IO_INTEGRITY_FLAG (1ULL << UBLK_INTEGRITY_FLAG_OFF)
> +
>  /*
>   * ublk server can register data buffers for incoming I/O requests with a sparse
>   * io_uring buffer table. The request buffer can then be used as the data buffer
>   * for io_uring operations via the fixed buffer index.
>   * Note that the ublk server can never directly access the request data memory.
> -- 
> 2.45.2
> 

Thanks,
Ming